Maximization of the Figure of Merit of Alloy SixGe1-x

The dependence of maximums of figure of merit ((ZT)max) on thermoelectric quality factor (B) for thermoelectric SixGe1-x of n-and p-type conductivity with a charge carrier concentration of 3.2∙1026m-3 has been considered. The values of x are: 0.7, 0.72, 0.76, 0.8 and 0.83. For all samples, (ZT)maxappears at about 900°C. The (ZT)max–σ'(universal electrical conductivity) dependence allows us to assume with sufficient accuracy the mentioned maxima for other values of σ'(that is, for SixGe1-xwith other relative compositions as well. Thus, σ' can be used to predict of (ZT)max. With this approach, a coefficient of thermal conductivity (kL) is not required. σ'S2–S dependence is also considered (S –Seebeck coefficient). Experimental points and the averaged curve for a large number of samples calculated from the data of literature match well. The middle part of this dependence (1∙10-4≤S≤2.5∙10-4 V∙K-1) is well described by the parabolic empirical expression. And in the range 0≤S≤6∙10-4V∙K-1the equation of exponential type should be used. Experimental points in coordinates σ'−BS/S2(BS=σS2/BE, σ-specific electrical conductivity, BE –electronic quality factor) are well located on a straight line for all x in n-and p-SixGe1-x ,except for some points for p-Si0.7Ge0.3. The dependence σ'−BS/S2have the form of a straight line with a slope of 1.347∙108 Sim∙W-1∙K-2.Short Communication